This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-73964 filed on Mar. 13, 2000.
1. Field of the Invention
The present invention relates to an electronic part packaging method in which an electronic part is wire bonded to wiring portion.
2. Description of the Related Art
In a conventional packaging method, generally, a conductive jointing material such as a conductive adhesive or solder is arranged over a ceramics substrate having a wiring portion plated on its surface with copper or silver, and an electronic part such as an IC chip is mounted on the conductive jointing material. After that, the wiring portion and the electronic part are then electrically connected by wire bonding with gold.
In this packaging method, jointability or wire-bondability is poor between the wiring portion and the gold wire. In JP-A-10-112471 discloses a method for retaining the wire-bondability by mounting the electronic part such as the IC chip over the conductive jointing material, subsequently by forming a gold bump over the wiring portion by the ball bonding, and by wire-bonding the wiring portion through the gold bump.
However, the packaging method of the conventional method is troubled by problems that the surface of the wiring portion is contaminated with the conductive jointing material, such as the bleeding of the conductive adhesive (i.e., the phenomenon that the component in the resin contained in the conductive adhesive is not hardened but flows out), or the outflow of a solder flux, or the oxidation of the surface of the wiring portion by the heating at the soldering time or at the conductive adhesive hardening time.
Thus, in the conventional method, when the gold bump is formed at the wire bonding portion in the wiring portion, the jointability between the gold bump and the wiring portion is worsened by the aforementioned contamination of the wiring portion surface so that the wire bondability at the wiring portion is deteriorated.
An object of the present invention is to provide an electronic part mounting method for wire bonding a wiring portion of a wiring substrate and an electronic part mounted on the substrate through a conductive jointing material in which the contamination of the wiring portion with the conductive jointing material is prevented, thereby improving the jointability between the substrate member and the wiring portion.
According to the present invention, a wire bonding pad is formed before a conductive jointing material is arranged over a wiring substrate.
Thus, the problem of the contamination of the wiring portion with the conductive jointing material is intrinsically avoided.
Further, the conductive jointing material is arranged and an electronic part is mounted after the pad is formed, so that a time period until the pad is formed is shortened. Therefore, a time period, for which the surfaces of the wire bonding portions on the wiring portions are exposed, is shortened, thereby suppressing the oxidation of the surfaces to the minimum. Accordingly, the contamination of the wiring portions with the conductive jointing material is prevented to improve the jointability between the pad or the substrate member and the wiring portions.